Steam reaching 5psi

Hello looking for some guidance i have a Crown boiler bsi103 and the psi is reaching 5psi sometimes more. I started researching and found that the pressuretrol might be the issue so I ordered one to have just in case.

The pressuretrol is set to 1psi on the main and .5 on the diff but the pressure still climbs to 5psi when the heat is on. I took off the pressuretrol and cleaned out the pigtail which was dirty but not fully clogged reassembled and same result, boiler goes to 5psi. I had the new pressuretrol and tried that with the same settings 1psi for main and .5 for diff but again same result.

I thought let me drain the boiler fully and found the drain valve is clogged with water dribbling out. Im planning on replacing the drain valve after work, refilling turning on to get hot and drain a few times to get it cleaned out.

Could this be the issue on why its reaching 5psi? Is there an additive I should get to help clean the boiler out?

Any help would be highly appreciated